Always follow flake-parts' nixpkgs-lib input?

[srid]

Tip

tldr; Why not do this in every repo that uses flake-parts ? srid/haskell-template@b7c6606

flake-parts has its own nixpkgs input:

flake-parts/flake.nix

Line 5 in 567b938

nixpkgs-lib.url = "https://github.com/NixOS/nixpkgs/archive/356624c12086a18f2ea2825fed34523d60ccc4e3.tar.gz"; # 12228ff1752d7b7624a54e9c1af4b222b3c1073b /lib from nixos-unstable

While it calls it nixpkgs-lib, the actual input refers to the whole nixpkgs repo which is pretty large. This leads to yet another fetch of nixpkgs thus slowing down (due to fetch and extract of nixpkgs) the initial eval of nix commands like nix develop.

Would it not make sense for user flakes to do the following always?

    flake-parts.url = "github:hercules-ci/flake-parts";
    flake-parts.inputs.nixpkgs-lib.follows = "nixpkgs";

Thus reducing the number of nixpkgss in the flake.lock file, viz.:

diff --git a/flake.lock b/flake.lock
index 7ebc7b7..8e74a25 100644
--- a/flake.lock
+++ b/flake.lock
@@ -2,7 +2,9 @@
   "nodes": {
     "flake-parts": {
       "inputs": {
-        "nixpkgs-lib": "nixpkgs-lib"
+        "nixpkgs-lib": [
+          "nixpkgs"
+        ]
       },
       "locked": {
         "lastModified": 1722555600,
@@ -64,18 +66,6 @@
         "type": "github"
       }
     },
-    "nixpkgs-lib": {
-      "locked": {
-        "lastModified": 1722555339,
-        "narHash": "sha256-uFf2QeW7eAHlYXuDktm9c25OxOyCoUOQmh5SZ9amE5Q=",
-        "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs/archive/a5d394176e64ab29c852d03346c1fc9b0b7d33eb.tar.gz"
-      },
-      "original": {
-        "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs/archive/a5d394176e64ab29c852d03346c1fc9b0b7d33eb.tar.gz"
-      }
-    },
     "root": {
       "inputs": {
         "flake-parts": "flake-parts",

[brsvh]

Maybe user should be prompted to do so in the Getting Started section of the document and in the default template.

flake-parts/template/default/flake.nix

Lines 5 to 6 in 3d04084

	flake-parts.url = "github:hercules-ci/flake-parts";
	nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";

[roberth]

It wasn't always, but now it's only the lib tree of Nixpkgs.

$ curl -L https://github.com/NixOS/nixpkgs/archive/a5d394176e64ab29c852d03346c1fc9b0b7d33eb.tar.gz | wc -c
[...]
244736

=> quarter of a megabyte.